High current electric switch with arc chute interlocked with movable contact,and spring driving means



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Arra/P/vfy Feb. 17, 1970 A. R. NoRDEN 3,496,319

' HIGHQCURRENT ELECTRIC SWITCH WITH ARC CHUTE INTERLOCKED l ITH MOVABLE CONTACT, AND SPRING DRIVING MEANS Filed Dec. 7.. 1966 3 sneet-sneet s United States Patent O U.S. Cl. 200-146 18 Claims ABSTRACT F THE DISCLOSURE There is provided a high current electric switch which has a stationary fuse and fuse holder assembly, a quickbreak and quick-make mechanism, stationary main and movable contacts and movable main and auxiliary contacts actuated by said mechanism, an arc chute in which said auxiliary contacts engage and disengage each other and an interlock between said movable main contact and the companion auxiliary contact which prevents engagement of the movable main contact with the companion main contact unless said arc chute is in position, there being means associated with the arc chute to release the interlock when the arc chute is in position and the auxiliary movable contact is being closed, said last mentioned means including part of the arc chute which also acts as a barrier to prevent arcing to the main movab-le contact when the auxiliary contacts are being disengaged.

This invention is related to electric switches and is par ticularly adapted to fusible, bolted pressure contact, service entrance switches.

High current, service voltage, switches are well known. Many of them have auxiliary arcing tips through which contact is rst made on closing, and last made on opening of the switch. Many of them have an arc chute or enclosure about each set of auxiliary arcing tips to contain and extinguish the arc which is developed on opening and closing the set of contacts. However, in many of these switches, the arc can blow from the auxiliary arcing tips to the main contacts.

It is, therefore, an object of this invention to provide a switch having arc chutes which preclude the blowing of an arc from the auxiliary arcing tips to the main contacts.

Some of these known switches have a quick make, quick break operating mechanism. However, these, once thrown towards close, will close or try to close regardless of the condition of the switch or the load circuit connected thereto. Should an excess in current be drawn, the electrodynamic forces developed will tend to throw open the switch, violently reversing the direction of movement of the operating handle with probable injury to the operator.

It is, therefore, another object of this invention to provide a switch having a quick make, quick break operation, which will only close its main contacts if both the switch is fully assembled and the load circuit does not contain :an overload which exceeds a predetermined magnitude, and which will limit and cushion any reversal in the direction of movement of the operating handle.

f'ce

A feature of this invention is the provision of a high current switch having a set of main contacts and auxiliary arcing tips for each line, and an arc chute enclosing each respective set of auxiliary arcing tips during their make and break operation, said arc chute including means blocking the blowing of any arc to the main contacts.

Another feature of this invention is the provision of a high current switch having a main moving contact and an auxiliary moving arcing tip carried thereby by interlock means, said interlock means precluding closing of the main contact until and unless the arcing tip has fully closed.

Yet another feature of this invention is the provision of a high current switch having a main moving contact and an auxiliary moving arcing tip carried thereby by interlock means, said interlock means precluding closing of the main contact until and unless the arcing tip has closed to sense the load current and has determined that there is not an overload which exceeds a predetermined magnitude.

These and other objects, features and advantages of the invention will become apparent from the following specication taken in conjunction with the accompanying drawing in which:

FIG. 1 is a perspective view of an embodiment of this invention, showing the switch in its open position, and with one arc chute removed for the purpose of illustration;

FIG. 2 is a right side detail view of the contact assemblies, showing the contacts in their fully open disposition;

FIG. 3 is a left side detail view of the contact assemblies, showing the auxiliary arcing contacts in closed disposition and the main contacts still open, all with the left half of the arc chute removed for the purpose of illustration;

FIG. 4 is a left side detail view of the contact assemblies in their fully closed positions, with the left half of the arch chute removed for the purpose of illustration;

FIG. 5 is a front detail view of the switch operating mechanism;

FIG. 6 is a front detail view of the switch operating mechanism in the switch closed position; and

FIG. 7 is a cross-sectional view of FIG. 6 taken along the plane 7-7.

The switch which is shown in FIG. 1 is supported on a frame provided by two rear upstanding angles 12 and 14, a front plate 16, and two side plates 18 and 20. An upper dielectric back panel 22 is mounted to and between the angles 12 and 14, as by a plurality of bolts and nuts 24. A lower dielectric back panel 26 is mounted to and between the angles 12 and 14, as by a plurality of bolts and nuts 28.

Three lines or phases are here shown as being simultaneously switched. Each phase includes: A line terminal 30, which is secured to and between two angles 32, 32, as by nuts and bolts 34, and which angles are secured to the upper dielectric panel 22, as by a plurality of nuts and bolts 36. An upper fuse terminal 38, which is secured to and between two angles 40, 40, as by a plurality of nuts and bolts 42, and which angles are secured to the upper dielectric panel 22, as by a plurality of nuts and bolts 44. A lower fuse and load terminal 46, which is secured to and between two angles 48, 48, as by a plurality of nuts and bolts 50, and which angles are secured to the lower dielectric panel 26, as by a plurality of nuts and bolts 52. A

fuse 54 has` an upper terminal 56 which is secured to the upper fuse terminal 38, as by a plurality of nuts and bolts 58, and a lower terminal 60 which is secured to the lower fuse terminal 46, as by a plurality of nuts and bolts 62. The various angles 32, 40 and 48 each have a plurality of ns 64 formed thereon for rapid heat radiation.

As best seen in FIGS. 2, 3, and 4, a main moving contact 66 comprises a pair of bars 68 which are pivotally mounted to and astride the upper fuse terminal by a lower cross-shaft 70. The pair of bars 68 is also provided with an upper cross-shaft 72 and a cross-rod 74. The right end of the lower cross-shaft 70 is integral with a crank 76, exterior to the right bar, having a short arm 78 and a long arm 80. The distal end of the long arm 80 terminates in a right angle 82 which is secured, as by a plurality of nuts and bolts 84, to a dielectric cross-bar 86. The left end of the lower cross-shaft 70i is threaded into a nut 88, exterior tothe left bar, which is fixed to the left bar, as by a machine screw 89. The right end of the upper cross-shaft 72 is integral with a crank 90, exterior to the right bar, having a short arm 92. The left end of the cross-shaft is threaded into a nut 94, exterior to the left bar, which is xed to the left bar, as by a machine screw 95. The distal ends of the short arms 78 and 92 are interconnected by a connecting rod 96. Downward movement of the connecting rod, and associated rotation of the cranks 76 and 90 and their respective cross-shafts 70 and 72 draws the pair of bars closer to each other.

In the main contact open position, shown in FIG. 2, the connecting rod 96 is in its upper position. In the intermediate position, shown in FIG. 3, the bars 68 are swung upwardly about the lower cross-shaft 70. The lower corner '98 of the terminal 30 is cut away to clear the bars in the intermediate position. The connecting rod remains in its upper position. In the fully closed position, shown in FIG. 4, the bars '68 are swung upwardly further to overlap the terminal 30. A notch 100 is cut into 'the terminal 30 to receive the upper cross-shaft 72. The connecting rod is in its lower position, and the bars 68 are clamped onto the terminal 30 and a terminal 38.

A relatively movable, auxiliary arcing contact assembly 102 is carried by each main moving contact 66. A lixed, auxiliary arcing contact assembly 104 is secured to each line terminal 30. The assembly 104 includes a pair 0f spring blades 106 which are respectively secured to each side of the terminal 30, as by a plurality of nuts and bolts 108. The distal ends of the blades each have a reflux bend 110 therein to form a female contact. The assembly 10-2 has an outline which approximates a question mark. The upper end 112, which serves as the male contact, is advantageously made of a solid bar. The lower end 114 is bifurcated, and is advantageously made of a pair of bars secured to the upper end, as by a plurality of nuts and bolts 116. The lower end 114 is pivotally mounted between the bars 68 -by the cross-rod 74 passing through a journal 118 mounted through the bars. A second dielectric cross-bar 120 is secured to each of the pair of bars 68, as by a plurality of machine screws 122. A compression spring 124 is mounted 4on one leg of a U-shaped guide 126. The reflexed end of the guide and the lower end of the spring are disposed in a blind bore 130 in the crossbar 120. The upper end of the spring is disposed in a notch 132 out into both bars 114, while the upper ends of the guide pass beyond the notch between the pair of bars 114. The spring is thus captured.

A pair of latches 134 are respectively mounted to the upper ends of the bars 68. Each latch 134 is pivoted to the bar 68, as by a machine screw 136. An elongated hole 138 is cut into the latch to pass the shank of a machine screw 140, while the head of the screw 140` precludes lateral movement of the latch. The upper portion 142 of the latch is bent over to form a camming surface. A hairpin spring 144 is disposed with its reflex portion under the head of the screw 136, and its legs between the cam 142 and the screw 140, to bias the latch upwardlly. A

crosspin 146 is secured through the upper part of the lower end portion 114 of the movable arcing contact assembly 102. A hook 148 is formed into each latch 134 and this hook is normally biased upwardly by the spring 144 when the switch is in its open position to engage behind the cross-pin 146. When the latch is so engaged, the main contact bars 68 cannot swing upwardly without similar movement of the movable arcing contact assembly 102. The compression spring 124 biases the moving auxiliary arcing contact 114 into abutment with the shaft 72 of the crank 90.

An arc chute assembly 150 is Secured to each line terminal 30. A U-shaped bracket 152 is secured to the edge of the terminal 30, as by a plurality of machine screws 154. A pair of chute halves 156 are secured to the bracket, as by a plurality of machine screws 158, and to each other, as by a plurality of nuts an-d bolts 1'60. The oair of chute halves together form a hollow enclosure in which the making and breaking of the auxiliary arcing contacts is performed. The halves have mutually abutting surfaces at portions 162, 164, 166 and 168. The female contact 104 projects into the enclosure between the portions 166 and 16S. The male contact 102 is movable into this enclosure between the portions 164 and 168. A plurality of grooves are formed into the inner walls of the chute halves to support a plurality of V-notched arc extinguishing plates 170. The portion 168 projects downwardly and serves as a cam which rides against the camming surface 142 of the latch 134 when the moving contacts 66 and 102 are swung upwardly from the open position of FIG. 2 to the intermediate position of FIG. 3. The male contact 102 passes into the enclosure, between the bifurcations of the V-notched plates 170, above the portion 168 into the female contact 110 until it abuts the edge of the terminal 30. Normally, each portion 168 will cam its respective latch 134 downwardly releasing the movable main contact assembly 6'6 for movement independently of the auxiliary arcing contact assembly 102. However, should any one of the arc chute halves 156 be missing from any of the terminals 30, then none of the contact assemblies `66 will move beyond the intermediate position of FIG. 3, since all of the main contacts are secured to the second dielectric cross-bar 120.

Any arcing between the auxiliary arcing contacts 104 and 102 as they make or break will be blocked by the re spective portions 168 of the arc chute from the main contact assembly 66. Any ionized gas will be drawn up between the plates 170 and will be blown out the top of the arc chute between the projections 162 and 164. On break motion particularly, when the arcing contacts '[irst separate, the portion 168 ensures that the lowest potential path for the arc is between the arcing contacts, rather than between one arcing contact and the other main contact.

The rst and second dielectric cross-bars 86 and 120 are interconnected by a pair of toggle assemblies 172. Each toggle assembly includes a cam 174 which is pivotal- 1y mounted at its lower end, as by a capped machine screw 176, to the cross-bar 86, and which has a notch 178 at its upper end. An arrn 180 is pivotally mounted at its upper end, as by a capped machine screw 182, to the cross-bar 120, and is pivotally mounted at its lower end, as by a spooled rod 184, to the middle of the cam 174. A tension spring 186 is secured to and between the screws 182 and 176, and around the spooled rod 184. In the locked position of the toggle assemblies shown in FIGS. 2 and 3, the notch 178 of the cam sits on the cap of the screw 182. A pair of striker assemblies 188 are secured to the upper dielectric back panel 22 in line with the respective toggle assemblies. Each striker assembly includes a bolt 190 secured to the panel 22 and a cap 192. When the moving main contact assembly 6'6 moves from the intermediate position of FIG. 3 to the closed position of FIG .4, the cap 192 of the striker assembly abuts the edge 0f the Cam 174, moving the pivot 184 Over Center against the bias of the spring 186, breaking the toggle, and per mitting the cross-bar 86 to move upwardly towards the cross-bar 120. Upward 4movement of the cross-bar 86 swings the crank arm 80 upwardly and the connecting arm 96 downwardly; rotating both cranks 76 and 90 to clamp the bars 68 tightly against the terminal 30 and the terminal 38.

Quick make and break operation of the switch is provided by an operator assembly 200. The operator assembly includes a shaft 202 which is journaled through the front plate 16 to an intermediate plate 204 and which plate is secured to the side plate 18, as by nuts and bolts 206. A handle 208 is secured to the shaft 202, as by a machine screw 210. A charging spring assembly couples rotation of the shaft 202 to movement of the dielectric cross-bar 86. The charging spring assembly includes a bracket 212 which is secured at one end to the cross-bar 86, as by a plurality of nuts and bolts 214, and at its other end is adapted to interlock with a hook 216 on the end of a detent 218. The bracket is pivotally secured to a clevis 220, as by a pin 222. The clevis is integral with a cap 224 and a stud 226. The cap is secured to the top of the tube 228, as by a pin 230 through the stud and the tube. The bottom of the tube 228 rests on a shoulder 232 of a spool 234 and is secured thereto, as by two pins 236. A cup shaped washer 238 also sits on the shoulder 232. A helical compression spring 240 is disposed on the tube 228 and is captured between the plate 224 and the washer 238. A rod 242 is disposed through a longitudinal bore 244 in the spool. The lower end of the rod is threaded and is secured to a convoluted washer 246 by a washer 248 and a nut 250. A helical compression spring 252 is disposed on the rod 242 and is captured between the top of the spool 234 and a washer 254 and a cross-pin 256 through the top of the rod. A cup 258, having a longitudinal bore 260 which clears the spool and a shoulder 262 which engages th'e washer 238, is supported on the convoluted washer 246. Two crank arms 264 `and 266 are secured to the shaft 202, as by welding, and are pivotally secured to the cup 258, as by pins 268 and 270 respectively.

The detent 218 is pivotally mounted to the front plate 16, as by a nut and bolt 272, and is limited in its swing by a pin 274 xed to said detent and projecting through a relatively larger hole 276 in the front plate. An arm 278 is pivotally secured at one end to the detent 218, as by a nut and bolt 280, and at its other end to one end of an arm 282 by a roller, a stud and a C spring 284. The other end of the arm 282 is pivotally secured to the front plate 16, as by a nut and bolt 288. A tension spring 290 is connected to and between the arm 282 and the front plate 16 to bias the detent 218 towards the bracket 212. A right angle 292 is secured to the arm 266, as by a plurality of machine screws 294 and has a foot portion 296 which is disposed under the roller 284.

When the switch is in its normal open position, the end of the bracket 212 is under the hook 216 of the detent 218. Upward rotation of the handle 208, towards the closed position, swings the brackets 266 and 264 upwardly and slides the cup 258, the washer 262, the spring 240, the clevis 220 and the bracket 212 upwardly to abut the bracket against the hook 216. Further rotation of the handle compresses the spring 240 against the clevis, and when the spring is fully compressed providing a direct drive, until the foot portion 296 engages the roller 284 to swing the detent 218 away from the bracket 216, therebly releasing the bracket from the hook. The now released compressed spring res the bracket 212, the dielectric cross-bar 86, the toggled locked thereto dielectric cross-bar 120, the main moving contact assemblies and the auxiliary arcing moving contact assemblies 102 upwardly. On normal operation, sequentially, the auxiliary male contact 112 will mate with the auxiliary female contact 110, the arc chute portion 168 will strike open the latches 134, the main Contact bars 68 will over-lap the terminal 30, the striker 192 will break the toggle 172, and the dielectric bar 86 will rotate the cranks 76 and 90 to clamp the bars 68 on the terminal 30 and the terminal 38.

If one or more of the arc chute halves 56 is missing, the respective latch 134 will not be opened and the switch will halt in the intermediate open position of FIG. 3.

If a short circuit condition should exist at the instant of closing of the arcing contacts 112 and 110, the flow of current creates electrodynamic forces having a direction which opposes the closing force of the Spring 240 and the momentum of the high inertial mass of the moving contacts.

In the case of a relatively less severe short circuit, these electrodynamic forces are insufficient to prevent the normal closing sequence of the switch. The moving arcing contacts 112 will be driven into engagement with the respective stationary arcing contacts 110 by the respective latches 134 engaged with their respective cross-pins 146. Subsequently, the latches will be disengaged from the cross-pins by the respective camming portions 168 of the arc chutes and the main moving contacts will close onto the main stationary contacts. In due course, depending on the current and the fuse ratings, the fuses will blow.

In the case of a very severe short circuit, these electrodynamic forces will equal or exceed the closing force of the spring 240 and the momentum of the high inertia mass of the moving contacts. Under such conditions, the fuses will blow within 1/2 cycle, while more than 1/2 cycle will be required to either drive the moving arcing contacts in their closing direction from the commencement of ma-ting with the stationary arcing contacts to the point of disengagement of the latches 136 from their respective cross-pins, or to arrest and reverse the direction of movement of the high inertia mass of the moving contacts driven by the spring 240. Therefore, within this 1/2 cycle the fuses will blow; and the light springs 124 will be compressed and the moving contacts will be arrested by the cross-pins pushing against the latch hooks 148 so that the latches 136 will not reach the camming portions 168 and will not Ibe disengaged from their respective cross-pins, and the main moving contacts will not mate with the main stationary contacts. Should the electrodynamic forces exceed the driving force, and the moving contacts be thrown back, such forces will be shock-absorbed and cushioned by the compression of the spring 240, and will not be directly transmitted to the handle.

When lthe switch is in its normal closed position, downward rotation of the handle 208 towards the open position, swings the brackets 266 and 264 downwardly and slides the cup 258, the convoluted washer 246, and the rod 242 downwardly, compressing the inner spring 252. When the spring 252 is fully compressed, the handle 208 is in direct drive with the clevis 220 and swings the bracket 212 downwardly, swinging the dielectric cross-bar 86 downwardly and locking the toggles 172. This releases the compressed spring 252 which now fires the bracket 212 and the moving contact assemblies 66 and 102 downwardly. A ramp 298 is formed on the corner of the -detent above the hook 216 so that the bracket 212 cams the detent aside as it moves downwardly to the open position. It should be noted that when the dielectric crossbar 86 is swung downwardly, it rotates the cranks 76 and to unclamp the bars 68 from the terminal 30. At this time the end 112 of the moving auxiliary arcing contact is abutting the edge of the terminal 30, and the compression spring 124 ybiases the dielectric cross-bar 120 and the main moving contact bars 68 away from the terminal 30. In the event that a chute is missing and the moving contact is halted in the intermediate position of FIG. 3 with the toggle unbroken, on opening movement the handle will swing 4the moving contact bars downwardly withinvention may be embodied otherwise than as herein specifically illustrated or described, and that certain changes in the form and arrangement of parts and in the specific manner of practicing the invention may be made without departing from the underlying idea or principles of the invention within the scope of the appended claims.

What is claimed is:

1. A high current switch comprising a stationary fuse and fuse holder assembly, a stationary main contact in series with said fuse of said assembly; a stationary auxiliary arcing contact electrically connected to said stationary main contact; a movable main contact adapted to move from an open main switch disposition whereat said main contacts are spaced apart to a closed main switch disposition whereat said main contacts are mated; an auxiliary arcing contact electrically connected to said movable main contact and lmechanically carried thereby in vertical alignment therewith and movable from an open auxiliary switch disposition whereat said auxiliary conA tacts are spaced apart to a closed auxiliary switch disposition whereat said auxiliary contacts are mated; and an arc chute substantially enclosing said stationary auxiliary arcing contact, and also enclosing the mating portion of said movable auxiliary arcing contact at such time as said movable auxiliary arcing contact to draw an arc therebetween, said arc chute having an upper passage for the flow of ionized gases therethrough when an arc is drawn therein and having a barrier portion which during such separation is disposed between the stationary auxiliary arcing contact and any portion of the moving main contact which is as close to said stationary auxiliary arcing contact as the closest portion of the movable auxiliary arcing contact; whereby to preclude travel of the arc from said arcing contacts to said movable main contact;

interlock means intercoupling said movable main contact and said movable auxiliary arcing contact against relative movement, said interlock means being operable by at least a part of said barrier of the arc chute thereby permitting the mating of said auxiliary arcing contacts and precluding the mating of said main contacts; and interlock release means for releasing said interlock means after said auxiliary arcing contacts have mated thereby permitting relative movement between said movable main and arcing contacts, and consequent mating of said main contacts.

2. A switch according to claim 1 further including interlock means intercoupling said movable main contact and said movable auxiliary arcing contact against relative movement, said interlock means being operable by at least a part of said barrier of the arc chute thereby permitting the mating of said auxiliary arcing contacts and precluding the mating of said main contacts and interlock release means for releasing said interlock means which are effective only in the presence of said arc chute thereby permitting relative movement between said movable main and arcing contacts, and consequent mating of said main contacts.

3. A high current switch comprising a stationary fuse and fuse holder assembly, a stationary main contact in series with said fuse of said assembly; a stationary auxiliary arcing contact electrically connected to said stationary main contact; a movable main contact adapted to move from an open main switch disposition whereat said main contacts are spaced apart to a closed main switch disposition whereat said main contacts are mated; an auxiliary arcing contact electrically connected to said movable main contact and mechanically carried thereby in vertical alignment therewith and movable from an open auxiliary switch disposition whereat said auxiliary contacts are spaced apart to a closed auxiliary switch disposition whereat said auxiliary contacts are mated; and an arc chute substantially enclosing said stationary auxiliary arcing Contact, and also enclosing the mating por tion of said movable auxiliary arcing contact at such time as said movable auxiliary arcing contact to draw an arc therebetween, said arc chute having an upper passage for the flow of ionized gases therethrough when an arc is drawn therein and having a barrier portion which during such separation is disposed between the stationary auxiliary arcing contact and any portion of the moving main contact which is as close to said stationary auxiliary arcing contact as the closest portion of the movable auxiliary arcing contact; whereby to preclude travel of the arc from said arcing contacts to said movable main contact; a stationary main terminal spaced from said stationary main contact; said movable main contact being pivotally mounted at one end thereof to said stationary main terminal, and the other end thereof being adapted to engage said .stationary main contact; said stationary auxiliary arcing contact being xedly mounted to said stationary main contact; said arc chute having an enclosure into which said stationary auxiliary arcing contact is xedly disposed, and an aperture through which the mating portion of said movable auxiliary arcing contact is adapted to pass while said other end of said stationary main contact passes outside said enclosure; interlock means intercoupling said movable main contact and said movable auxiliary arcing contact against relative movement; said interlock means being operable by at least a part of said barrier of the arc chute thereby permitting the mating of said auxiliary arcing contacts and precluding the mating of said main contacts; and interlock release means supported by said arc chute for releasing said interlock means only in the presence of said arc chute and after said auxiliary arcing contacts have mated thereby permitting relative movement between said movable main and arcing contacts, and consequent mating of said main contacts. y

4. A switch according to claim 3 -wherein said stationary main contact comprises a single bar; said movable main contact comprises a pair of bars pivotally mounted at said one end thereof astride said stationary main terminal, and adapted to have said other ends thereof swung astride said stationary main contact to mate therewith; and means carried at least in part by said movable main contact for clamping said pair of bars on said stationary main terminal and said stationary main contact when said bars are disposed astride said stationary main contact.

5. A switch according to claim 4 wherein said movable auxiliary arcing contact is pivotally mounted at one end thereof to and between said pair of bars of said movable main contact; bias means biasing the other mating end of said movable auxiliary arcing contact and the mating end of said movable main contact apart; xed stop means limiting movement of Said mating end of said movable auxiliary arcing contact under the bias of said bias means away from said mating end of said movable main contact towards the said stationary auxiliary arcing contact; said interlock means limiting movement of said mating end of said movable main contact, against the bias of said bias means, towards said stationary contact.

6. A switch according to claim 5 wherein said bias means biases said movable main contact for movement away from said stationary main contact when said main contacts and said auxiliary contacts are respectively mated, which movement is precluded by said clamping means clamping said main contacts together.

7. A switch including a stationary fuse and fuse holder assembly, a stationary main contact in series with said fuse of the assembly, a movable main contact and operating means including a rotary control shaft, lever actuated means coupling said rotary shaft to said main contact for making and breaking said main contacts; said operating means including a rst bias means coupled between said lever means and said movable main contact, rst detent means for precluding movement of said movable main contact, whereby initial rotation of said control shaft in a first direction is effective to strain Said first bias means against said first detent means and further rotation of said control shaft in said first direction is effective to release said first detent means from said first bias means and the strain in said first bias means is relieved by moving said movable main contact towards said stationary main contact, and a second bias means coupled between said lever means and said movable main contact, second detent means for precluding movement of said movable main contact, whereby initial rotation of said control shaft in a second direction opposite to said firstdirection is effective to strain said second bias means against said second detent means and further rotation of said control shaft in said second direction is effective to release said second detent means from said second bias means and the strain in said second bias means is relieved by moving said movable main contact from said stationary main contact.

r8. A switch according to claim 7 wherein said first bias means is a compression spring and said second bias means is a compression spring.

9. A switch according to claim 8 wherein said second compression spring is disposed coaxially of and surrounded by said first compression spring.

10. A switch according to claim 9 wherein said second detent means is a toggle assembly coupled between said movable main contact and said second spring.

11. A switch according to claim 7 wherein said first bias means is a compression spring mounted on a first tubular guide; the upper end of said guide being pivotally connected to an arm assembly which is releasably engaged by said first detent means and is connected to said movable main contact by a toggle assembly; said toggle assembly being normally in a locked disposition when the switch is open and in an unlocked disposition when the switch is closed; a sliding assembly disposed on said tubular guide with said first compression spring being disposed between said arm assembly and said sliding assembly; a crank assembly coupling said operating shaft to said sliding assembly whereby rotation of said operating shaft in said first direction swings said crank assembly to slide said sliding assembly on said tubular guide to compress said first spring against said arm assembly; and wherein said second bias means is a compression spring mounted on a second guide and both are disposed within said first tubular guide; said second spring being disposed between an upper stop ori said second guide and a lower stop within said first guide, whereby rotation of said operating shaft in said second -direction swings said crank assembly to slide said sliding assembly to engage and move said second guide to compress said second spring between said upper stop on said second guide and said lower stop within said first guide, said toggle assembly serving as said second detent, and when in its unlocked disposition restraining said first tubular guide from significant movement until said toggle assembly is swung into its locked disposition.

12. A high current switch comprising a stationary fuse and fuse holder assembly, a stationary main contact in series with said fuse of said assembly; a stationary auxiliary arcing contact electrically connected to said stationary main contact; a movable main contact adapted to move from an open main switch disposition whereat said main contacts are spaced apart to a closed main switch disposition whereat said main contacts are mated; a movable auxiliary arcing contact electrically connected to said movable main contact and mechanically carried thereby from an open auxiliary switch disposition whereat said auxiliary contacts are spaced apart to a closed auxiliary switch disposition whereat said auxiliary contacts are mated; a stationary main terminal spaced from said stationary main contact; said movble main contact being pivotally mounted at one end thereof to said stationary main terminal, and the other end thereof being adapted to engage said stationary main contact; said stationary auxiliary arcing contact being fixedly mounted to said stationary main contact; interlock means intercoupling said movable main contact and said movable auxiliary arcing contact against relative movement, said interlock means permitting the mating of said auxiliary arcing contacts and precluding the mating of said main contacts until the auxiliary contacts are mated; and interlock release means for releasing said interlock means when said auxiliary arcing contacts have mated thereby permitting relative movement between said movable main and arcing contacts, and consequent mating of said main contacts.

13. A switch according to claim 12 where said stationary main terminal lcomprises a single bar; said stationary main contact comprises a single bar; said movable main contact comprises a pair of bars pivotally mounted at said one ends thereof astride said stationary main terminal, and adapted to have said other ends thereof swung astride said stationary main contact to mate therewith; and means carried at least in part by' said movable main contact for clamping said pair of bars on said stationary main terminal and said stationary main contact when said bars are disposed astride said stationary main contact.

14. A switch according to claim 13 wherein said movable auxiliary arcing contact is pivotally mounted at one end thereof to and between said pair of bars of said movable main contact; bias means biasing the other, mating end of said movable auxiliary arcing contact and the mating end of said movable main contact apart; fixed stop means limiting movement of said mating end of said movable auxiliary arcing contact under the bias of said bias means away from said mating end of said movable main contact towards the said stationary auxiliary arcing contact; said interlock means limiting movement of said mating end of said movable main contact, against the bias of said bias means, towards said stationary main contact.

15. A switch according to claim 14 wherein when said main contacts and said auxiliary arcing contacts are respectively mated, said bias means biases said movable main contact for movement away from said stationary main contact, which movement is precluded by said clamping means clamping said main contacts together.

16. A switch according to claim 12 further including spring means for driving said movable auxiliary arcing contact from said open disposition along a path to said closed disposition and Said movable main contact from said open disposition to said closed disposition, said spring means and said movable contacts developing a predetermined kinetic force at a point in said path whereat said movable auxiliary arcing contact has mated with said stationary auxiliary arcing contact but said interlock release means has not released said interlock means, whereby the passage of a current through said auxiliary arcing contacts in excess of a predetermined maximum will develop an electrodynamic force greater than said kinetic force to drive said movable auxiliary contact to said respective open disposition, and said movable auxiliary contact will carry said thereto interlocked, unmated, movable main contact to said respective open disposition.

17. A high current switch having companion stationary and movable contacts, an arc chute, companion stationary and movable auxiliary contacts engageable with and disengageable from each other in said arc chute, a releasable interlock between said movable main and auxiliary contacts comprising a pivoted member mounted on said movable main contact and biased to interlocking position, means on said movable auxiliary contact releasably engageable with said pivoted member in said interlocking position thereof whereby movement of said movable main contact toward closed position moves said auxiliary contact toward closed position, and means in the path of movement of auxiliary contact toward closed position engageable with said pivoted member for moving said member out of interlocking position.

18. A high current switch according to claim 17, wherein the are chute has a part which prevents anarc drawn in said chute from reaching the main movable contact and which includes said means in said path of movement of said movable auxiliary Contact.

References Cited UNITED STATES PATENTS Yarrick.

Wiktor 20G-146y Schwab 200-144 X Caswell et al. 74-97 Atwood ZOO-146 Ulrich 200-146 12 Atkinson 200-62 X Scheuermeyer 200-146 Latour 200-144 X Beach 200--146 Pokorny et al. 200-78 X Albright et al 200-l46 Fink et al. 200-62 X Mrenna et al. 20D-50.1v Engel 200-146 U.S. C1. X.R. 

